Within a number of industries, there is growing interest in the use of flexible and/or very thin substrates, for example, stainless steel, silicon wafers, glass, ceramic, polyimide and polyester films. Flexible and very thin substrates are too fragile to be handled freestanding in downstream manufacturing conditions, and must be supported on a suitable carrier to survive. After the fabrication processes are done, the substrate must be removable from the carrier undamaged, preferably at ambient temperature.
In the electronics industry, as one example, imaging displays, sensors, photovoltaics and RFIDs, increasingly require thin and/or flexible substrates for display applications for cell phones, personal digital assistants, iPADs, or TVs. An exemplary substrate is a very thin (100 μm) glass packed with functionalities. The glass is processed at 400° C. to depose thin film transistors (TFT) or at 350° C. to deposit indium tin oxide (ITO) as a transparent conductor. Due to the fragility of the glass and the harsh process conditions, this glass must be reinforced or protected by a more stable substrate during fabrication.
Uses such as this call for a high temperature stable adhesive that is easily and cleanly debondable, that permits temporary bonding at high processing temperatures, and that does not compromise handling or performance of the substrates. This is a drive particularly within the electronics industry. Development of such adhesives would allow existing fabrication methods, such as for semiconductors, active matrix thin film transistors, touch membranes, or photovoltaics, to use the currently installed base of manufacturing tools and machines. Most currently available temporary adhesives are not thermally stable at the maximum processing of the manufacturing steps, which can be as high as 400° C.
Adhesives suitable for high temperature temporary bonding applications, which can later be removed at room temperature without causing damage to the target component, would advance the use of thinner or more flexible substrates across various industries.